A modified combined-variable formula for calculating total cubic-foot volumes of trees was tested on data sampled from 11 species. This formula is: V = a3 + b3Db2Hc2 where V is the total, cubic-foot volume, D is the d.b.h. (o.b.), a3 is the regression constant, b3 is the regression coefficient and b2, and c are the coefficients obtained from the logarithmic or Schumacher formula: log V = a2 + b2 log D + c2 log H Compared with the standard combined-variable formula: V = a1 + b1D2H the modified formula gave small but consistent improvements in accuracy.